Isothermal Rolling Circle Amplification via Endonuclease Cleavage
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Solution Overview
Problem
Current nucleic acid amplification methods require temperature cycling, complex primer designs, and specialized instrumentation, making them costly and inaccessible for widespread, targeted, and sensitive amplification, especially at ambient temperatures.
Innovation Solution
Site-specific endonuclease guided rolling circle amplification methods that simplify primer requirements by using site-specific cleavage and complementary hybridization between a free 3′ end and a circular DNA probe for isothermal amplification, reducing the need for multiple primers and specialized equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional amplification methods (PCR, LAMP) are used, then amplification can be achieved, but temperature cycling or complex primer designs are required, increasing device complexity and operational difficulty
Solution Approach 1:
The patent extracts the temperature cycling step from the amplification process by using isothermal conditions. The phi29 DNA polymerase enables DNA synthesis at a constant temperature (30-37°C), eliminating the need for complex temperature cycling equipment and simplifying the operational process while maintaining amplification capability
Solution Approach 2:
The circular DNA probe serves multiple functions: it acts as both the template for amplification and the source of the rolling circle mechanism. This multi-functional design reduces the number of separate components needed, thereby reducing device complexity while maintaining ease of operation
2Reliability
If multiple primers are used for targeted amplification, then amplification specificity is improved, but primer design complexity and reagent costs increase
Solution Approach 1:
The circular DNA probe automatically provides the template for repeated synthesis rounds through its circular structure. The 3' end of the probe serves as both the starting point for DNA synthesis and the template for subsequent rounds, eliminating the need for multiple external primers while maintaining amplification specificity through the complementary base pairing between the probe and target sequence
Solution Approach 2:
The circular DNA probe is pre-designed with a specific sequence that is complementary to the target region. This preliminary design ensures that only the intended target sequence will be amplified, providing specificity without requiring multiple primers. The probe's circular structure is established beforehand to enable the rolling circle mechanism
3Measurement precision
If specialized instrumentation is used for amplification, then amplification accuracy is improved, but cost and accessibility worsen
Solution Approach 1:
The patent uses a disposable circular DNA probe that is inexpensive to synthesize and can be discarded after use. This eliminates the need for expensive, specialized instrumentation while maintaining amplification accuracy. The probe's short functional life (single-use) reduces the need for costly equipment maintenance and calibration
Solution Approach 2:
The patent replaces the mechanical temperature cycling system with a biochemical system based on the phi29 DNA polymerase's isothermal activity. This substitution eliminates the need for complex thermal cycling equipment while maintaining amplification accuracy through the enzyme's inherent temperature stability and processivity
4Productivity
If temperature cycling is used for denaturation and primer binding, then amplification efficiency is improved, but energy consumption and operational complexity increase
Solution Approach 1:
The patent changes the temperature parameter from cyclic variation to a constant isothermal condition (30-37°C). This parameter change enables the phi29 DNA polymerase to function continuously without the energy-intensive temperature cycling, while maintaining high amplification efficiency through the enzyme's processivity and the rolling circle mechanism's ability to continuously synthesize DNA
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach achieves high target specificity and sensitivity with minimal instrumentation and inexpensive reagents, enabling amplification at uniform temperatures, thus overcoming the limitations of existing methods.
Implementation Method 1
cleaving the substrate with the endonuclease; a phosphate group is present at the 5′ end of the cleaved substrate immediately adjacent to the free 3′ end
Implementation Method 2
contacting the cleaved substrate with a circular DNA probe under conditions that allow for hybridization between complementary sequences of the cleaved substrate and the circular DNA probe
Implementation Method 3
generating an amplified nucleic acid product by rolling circle amplification (RCA)
Data Source
AI summary
The disclosure provides methods and kits involving site-specific endonuclease guided rolling circle amplification (RCA). Nucleic acid substrates, optionally generated by hybridizing a guidance primer to a single stranded nucleic acid, are cleaved with a site-specific endonuclease. In the presence of the target site, endonuclease cleavage of the substrate generates a nucleic acid having a free 3′-hydroxyl end, which is allowed to hybridize to covalently closed circular DNA probe (“take-off probe”), and initiate a rolling circle amplification (RCA) reaction. The methods and kits may be used to detect the presence of a target nucleic acid sequence, including detection of single nucleotide polymorphisms, and may be used to assess methylation status of a desired sequence, assess zygosity and/or ploidy status. The methods and kits may also be used to detect nucleic acids associated or indicative of medical conditions or pathogenic organisms.